Extrusion

ABSTRACT

A metal extrusion process in which the force for extrusion of the metal through a die is derived, at least in part, by maintaining frictional engagement of the metal with passageway defining surfaces of a member which is moved towards the die such that frictional drag of the passageway defining surfaces urges the metal through the die. Apparatus for performing the method is disclosed, including having the capability of continuous feed.

llnited States Patent 1191 11 3,765,216 Green Oct. 16, 1973 EXTRUSION3,308,510 3/1967 Gabbrielli 425/224 1 1 m 1221212 11212 2111:2121; land3,415,088 12/1968 Alexander et al. 72/60 [73] Assignee: United KingdomAtomic Energy Authority, London, England [22] Filed: Feb. 23, 1972 [21]Appl. No.: 228,673

[30] Foreign Application Priority Data Mar. 12, 1971 Great Britain6,778/71 Jan. 26, 1972 Great Britain 3,668/72 [52] US. Cl 72/262,72/263, 72/271,

, v 425/224 [51] Int. Cl. B21c 33/00 58] Field of Search 72/60, 262,270, 72/271, 272, 273, 263; 425/224, 376

[56] v References Cited UNITED STATES PATENTS 2,845,656 8/1958Gabbrielli 425/376 Primary Examiner-Richard J. Herbst Attorney-Robert B.Larson et al.

[57] ABSTRACT A metal extrusion process in which the force for extrusionof the metal through a die is derived, at least in part, by maintainingfrictional engagement of the metal with passageway defining surfaces ofa member which is moved towards the die such that frictional drag of thepassageway defining surfaces urges the metal through the die. Apparatusfor performing the method is disclosed, including having the capabilityof continuous feed.

15 Claims, 11 Drawing Figures PATENTED EDT 1 6 I975 SHEET 1 []F PATENTEDam 1 s 1915 SHEET k 0F 5 EXTRUSION BACKGROUND OF THE INVENTION Thisinvention relates to the forming of materials by extrusion.

In extrusion a workpiece is subjected to pressure in a container so thatthe workpiece is extruded from the container through an orifice definingthe product cross section. Pressure may be applied on the workpiecemechanically, as in conventional extrusion by a ram acting on theworkpiece in a container. Alternatively, as in hydrostatic extrusion,liquid may be pressurised about the workpiece in the container to effectextrusion of the workpiece.

One feature which is a practical limitation in carrying out such anextrusion process particularly when applied to metals, is that thepressure required to carry out extrusion is dependent on the extrusionratio, the extrusion ratio being defined as the cross sectional area ofthe workpiece relative to the cross sectional area of the extrudedproduct.

Even in the case of easily worked metals high extrusion ratios can onlybe achieved by the application of prohibitively high pressures on theworkpiece in the container. The manufacture of containers which canwithstand such high pressures is difficult and costly.

It is an object of the present invention to provide an extrusion processin which this difficulty is avoided.

SUMMARY OF THE INVENTION In one aspect, the present invention provides ametal extrusion process in which the force for extrusion of the metalthrough a die means is derived, at least in part, by maintainingfrictional engagement of the metal with passageway defining surfaces ofa member which is moved towards the die means such that frictional dragof the passageway defining surfaces urges the metal through'said diemeans.

The frictional engagement may be maintained by holding against the metala member which is held stationary relative to the die means and whichhas a lesser metal engaging area than the moving member, such thatfrictional drag of the passageway defining surfaces of the movingmemberwith the metal predominates for urging the metal through the die means.The metal which is fed to the passageway defining surfaces may be solidbar or rod, or may be in powder form.

In conventional and hydrostatic extrusion, the size of workpiece whichcan be accomodated in the extrusion container governs the length ofextruded product which can be formed in a single operation. Theworkpiece diameter is limited by the extrusion ratio which can beachieved at the designed working pressure of the extrusion container.Therefore, increase of product length can only be achieved by increasein the length of the workpiece with consequent increase in the length ofthe extrusion container to contain the workpiece,which adds to thedifficulty and cost of manufacture of such containers.

It is a further object of the present invention to provide apparatus forcarrying out the process of the present invention, preferably with thecapability of handling a continuous feed.

Extrusion apparatus according to the invention comprisesfirst and secondmembers defining an elongate passageway therebetween, said first andsecond members being movable one relative to the other in the directionof the length of the passageway, an abutment member fixed relative tosaid second member to project into and block the passageway, meansdefining at least one die orifice leading from the passageway andassociated with the abutment member, means for continuously feedingmaterial to be extruded into the passageway at a point spaced from theabutment member, the amount of the surface area of the passagewaydefined by the first member which is movable towards the abutment memberbeing greater than the amount of the surface area of the passagewaydefined by the second member whereby material fed into the passageway ismoved by frictional drag with the surface of the passageway in the firstmember towards the abutment member and is thereby extruded through thedie orifice.

A particular form of extrusion apparatus in accordance with theinvention comprises a wheel member having an endless groove therein, ashoe member covering part of the length of the groove and forming apassageway therewith, an abutment member projecting from the shoe memberinto the groove and blocking one end of the passageway, the wheel memberbeing rotatable relative to the shoe member in the direction towards theabutment member, at least one die orifice associated with the abutmentmember, and means for feeding material to be extruded into the end ofthe passageway remote from the abutment member so that the .material iscarried along in the groove by frictional drag in the direction towardsthe abutment member and is thereby extruded through the dib orifice. Thedie orifice may be provided in the leading face of the abutment member.Alternatively the abutment member may be of solid form, the die orificebeing provided in the face of the shoe member in front of the abutmentmember. In the first case the abutment member may be provided with amultiplicity of die orifices in its leading face or in the latter case amultiplicity of die orifices may be formed in the face of the shoemember forward of the solid abutment member. In either case the dieorifices may be defined by die insert members fitted in housings.

A plurality of shoe members may co-operate with the groove at spacedintervals.

Our copending application Ser. No. 880,127 filed Nov. 26, 1969 in myname as inventor relates to extrusion apparatus in which a bulkcompressive stress is applied in material to be extruded so as to feedthe material into the region forward of the working face of a toolmember which is moved so that the material in this region is subjectedto an additional compressive stress and is formed through a die orificeassociated with the tool member under the influence of the additionalcompressive stress in combination with the bulk compressive stressacting in the material.

A preferred form of extrusion apparatus as disclosed in said copendingapplication Ser. No. 880,127 employs a rotary tool member having an endface with a tooth member projecting therefrom. The tool member isrotated about an axis transverse to the end face having the projectingtooth member so that the tooth member is moved in a circular path withits forward working face in pressure contact with material in the regionof the end face of the tool member. The material is subjected to a bulkcompressive stress to feed the material continuously into the region ofthe end face of the tool member. The material forward of the workingface of the tooth member is subjected to an additional compressivestress so that the material is formed through a die orifice associatedwith the tooth member under the influence of the additional compressivestress in combination with the bulk compressive stress acting in thematerial.

Apparatus in accordance with the present invention may be employed forthe pressure feeding of material into the region of the end face of thetool member in apparatus of the kind disclosed in said copendingapplication Ser. No. 880,127.

In the form of apparatus according to the present invention whichcomprises a rotary wheel member, material fed along the groove is workedby a rotary tool member of the kind disclosed in copending applicationSer. No. 880,127, the tool member being fitted in a housing in the shoemember with the end face of the tool member open to the region of thegroove adjacent the face of the abutment member.

DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now bedescribed by way of example with reference to the accompanying drawingsin which:

FIG. 1 is a part-sectional longitudinal elevation of extrusion apparatusin accordance with the invention,

FIG. 2 is an exploded isometric view of the apparatus shown in FIG. 1,

FIG. 3 is a modification of the arrangement shown in FIGS. 1 and 2,

FIG. 4 is a sectional elevation ofa further form of apparatus inaccordance with the invention,

FIGS. 5, 6, 7, 8 and 9 are details in isometric form of modifications ofthe apparatus of FIG. 4,

FIG. 10 is a sectional detail of a third form of apparatus in accordancewith the invention,

FIG. 11 is a section along the line XIXI in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The extrusion apparatus shownin FIGS. 1 and 2 comprises a wheel 1 rotatably mounted on a shaft 2. Thewheel 1 has a square cross-section circumferential groove 3 machinedaround its outer edge, the groove being therefore a square surface ofrevolution about the axis of the wheel. A shoe member 4 fits closelyagainst the edge of the wheel 1. An abutment member 5 formed on theunder side of the shoe member 4 projects into the circumferential groove3 and is complementary in shape to the groove cross section so as toblock the groove with a sliding fit. The abutment member 5 has anextrusion orifice 6. A chamber 7 integrally formed with the shoe member4 has a bore 8 connecting with the circumferential groove 3 in thewheel 1. A sealing block 9 formed on the underside of the shoe member 4at the opposite end to the abutment member 5 projects into and is aclose sliding fit in the circumferential groove 3 in the wheel 1.

Material 10 to be extruded is fed under pressure through the bore 8 ofthe chamber 7 and fills that part of the groove 3 in the wheel 1underneath the shoe member 4 between the abutment member 5 and thesealing block 9 of the shoe member 4.

The material to be extruded may be forced through the chamber 7 into thegroove 3 by a ram acting in the bore 8 of the chamber 7. After extrusionof the material within the chamber 7 the ram is withdrawn and furthermaterial is supplied to the chamber 7, for example, from a continuouscasting unit. Alternatively the material may be fed as powder eitherintermittently by a ram or continuously by screw feeders.

The wheel 1 is rotated clockwise as shown by the arrow 11 in FIG. 1. Thematerial 10 in the circumferential groove 3 beneath the shoemember 4 iscarried forward towards the abutment member 5 by the frictional drag ofthe walls of the circumferential groove 3. Thus pressure is generated inthe material in the circumferential groove 3, so that the material isextruded through the orifice 6 in the abutment member 5. Also therotation of the wheel 1 drags material under a transverse shearingaction from the bore 8 of the chamber 7 so that a continuous extrusionof the material is obtained. Material drawn from the chamber 7 byrotation of the wheel 1 is continually replaced by the continuous feedof fresh material into the chamber 7.

With powdered feed the pressure applied on the material in thecircumferential groove 3 results in compaction of the powdered material.Further compaction of the powdered material occurs during extrusionthrough the extrusion orifice 6 so that a solid extruded product isobtained.

The circumferential groove 3 in the wheel 1 in conjunction with the shoemember 4 may be regarded as forming a passageway or channel having fourwalls. The three walls of the channel defined by the side walls and baseof the circumferential groove 3 move continuously towards the abutmentmember 5. The fourth wall of the channel, defined by the under surfaceof the shoe member 4 is stationary. As described above the three movingwalls of the circumferential groove 3 carry the material 10 byfrictional drag, towards the abutment member 5. The material slides overthe stationary fourth wall formed by the under surface of the shoemember 4. Thus if the frictional coefficients are the same for all fourwalls and since the stationary wall formed by the under surface of theshoe member 4 is opposing the frictional drag applied on the material bythe base of the circumferential groove 3, in effect the frictional dragof the two side walls of the circumferential groove 3 carry the materialtowards the abutment member 5.

The resultant force acting on the material 10 in the direction towardsthe abutment member 5 is thus:

2.l.w.k.

where:

l the circumferential length of the groove 3 below the shoe member 4which is filled with the material to be extruded,

w the width of the side walls of the circumferential groove 3,

k= the shear strength of the material being extruded. This force of2.l.w.k. must produce a load on the face of the abutment member 5 of PAwhere P the pressure required for extrusion of the material A the crosssectional area of the abutment member 5 which is the same as the crosssectional area of the circumferential groove 3.

In the case of a groove 3 of square cross section A w and therefore PAPw Thus under extrusion conditions 2.1.w. Pw'

Therefore where Y= 2k the yield strength of the material. It followsthat This expression enables the calculation of the dimensionalparameters of apparatus as described above for extrusion of a selectedmaterial.

For example considering the extrusion of copper which may be taken ashaving a yield strength of 3 tons per square inch.

The use of a wheel 1 having a square cross section circumferentialgroove of inch side width and an extrusion orifice 6 in the abutmentmember 5 of 0.075 inches diameter results in an extrusion ratio ofapproximately 55 1 which will require an extrusion pressure of about 100tons per square inch. Therefore:

and

= approximately 17 inches If a shoe member 4 having a length of aboutone quarter of the circumference of the wheel 1 is employed this fixesthe required diameter of the wheel 1 at about 21 inches.

FIG. 3 shows a second arrangement for the continuous extrusion of bar.The arrangement of FIG. 3 is simi lar to that of FIGS. 1 and 2 andsimilar parts in the two arrangements are referred to by the samereference numerals. v

In the arrangement of FIG. 3 the chamber 8 is omitted from the shoemember 4. A bar 11 of feed material is.fed continuously into thecircumferential groove 3 in the edge of the wheel 1. The bar 11 iscontinuously car ried forward in the groove 3 beneath the shoe member 4towards the abutment member 5 and the leading end of the bar 11 iscontinuously extruded through the orifice 6 in the abutment member 5. Inthis case no external pressure feed is required for the bar 11 and thearrangement is particularly suitable for the extrusion of powderedmaterial which may be fed into the groove 3 by continuous tamping or bya screw feeder. A gravity feed may suffice although measures to ensurefree flow may be advisable. When starting operation with a new feed, apowdered material may not be mixed immediately by the moving surfaces.However, with assistance if necessary, the particles will ultimatelypack in a manner which renders frictional drag effective. For a solidfeed, such as the bar 11 a roller may be used immediately in advance ofthe shoe member 4 for pressing the bar into the groove.

The apparatus shown in FIG. 4 is of the same basic form as FIGS. 1 and 2and again similar parts are referred to by the same reference numerals.The apparatus of FIG. 4 comprises a wheel 1 rotatably mounted on a shaft2. The wheel 1 has a circumferential groove 3 machined around its outeredge. Two shoe members 4 are fitted closely against the edge of thewheel 1. An abutment member 5 is formed on the underside of each shoemember 4 projecting into the circumferential groove 3 on the wheel 1. Adie insert 6 is fitted in a housing 7 forward of the abutment member 5.The die insert 6 connects with an outlet passageway 8 leading throughthe shoe member 4. In use of the apparatus shown in FIG. 4 a bar 9 offeed material is fed continuously into the circumferential groove 3below each shoe member 4. The wheel 1 is rotated anti-clockwise as shownby the arrow 10. The walls of the circumferential groove 3 exert africtional drag on each of the bars 9 of feed material. Each bar 9 isdrawn along in the groove 3 below the corresponding shoe member 4towards the abutment member 5 on the shoe member 4. Thus pressure isgenerated in the material of the bars 9 within the circumferentialgroove 3 below the shoe members 4 and the leading end of each bar 9 isextruded through the die insert 6. The extruded product passes outradially through the outlet passageways 8.

Although FIG. 4 shows the use of two shoe members 4 in conjunction withthe wheel 1 a larger number of shoe members 4 can be employed dependingon the diameter of the wheel 1. For example three shoe members 4 may beused spaced at l20 intervals around the circumference of the wheel 1. Inproduction equipment there may be several wheels I mounted on a commonshaft each wheel 1 having a plurality of shoe members 4. An arrangementusing shoe members in diametrically opposed relationship serves tobalance the thrusts at the wheel member bearings of the radially inwardforces generated by the compression of material at the abutment member.

Each shoe member 4 may have a single die insert 6 as shown in FIG. 4.Alternatively each shoe member 4 may be fitted with a number of dieinserts 6. FIG. 5 shows two die inserts 6 arranged one in front of theother forward of the abutment member 5. FIG. 6 shows four smaller dieinserts 6 arranged in a group forward of the abutment member 5. Dieinserts having orifices of non-circular cross section may be employed.In FIG. 7 the die insert 6 has an orifice ll of rectangular formextending parallel to the face of the abutment member 5. In thisarrangement the length of the orifice 11 in the die insert 6 is governedby the width of the circumferential groove 3. In FIG. 8 the die insert 6has a rectangular orifice 11 which extends at right angles to the faceof the abutment member 5. The arrangement of FIG. 8 enables an orificeof greater length to be employed than in the arrangement of FIG. 7. FIG.9 shows a porthole die insert 6 enabling the extrusion of a tubularproduct.

In the arrangement of FIGS. 1 and 2 and of FIG. 3 the abutment member 5may be provided with a multiplicity of die orifices 6 which may be inthe form of die inserts fitted in housings in the abutment member 5.

FIGS. 10 and 1 1 are details of an extrusion apparatus again including awheel 1 having a circumferential groove 3 around its outer edge. A shoemember 4 is fitted closely against the edge of the wheel 1. An abutmentmember 5 is formed on the under side of the shoe member 4 projectinginto the circumferential groove 3 on the wheel 1. A radial drilling 12in the shoe member 4 forward of the abutment member 5 houses a rotarytool member 13. The lower end face 14 of the tool member 13 has a toothshaped projection 15 and a die insert 16 is fitted in the face 14 of thetool member 13. A guide member 17 having a wedge shaped base 18 with acylindrical boss 19 is fitted in the groove 3 of the wheel 1 in front ofthe abutment member 5.

In use of the apparatus of FIGS. 10 and 11 the wheel 1 is rotatedanti-clockwise relative to the shoe member 4 in the direction of thearrow 20 in FIG. 10. The walls of the groove 3 in the wheel 1 exert africtional drag on feed material 1 in the groove 3. Thus rotation of thewheel 1 feeds the material towards the abutment member 5 of the shoemember 4 and the guide member 17 distributes the material 21 into theregion of the lower end face 14 of the rotary tool member 13. An overallcompressive stress is also generated in the material 21 within thecircumferential groove 3 of the wheel 1 below the tool member 13.Rotation of the tool member 13 in the direction of the arrow 22 in FIG.1 1 drives the projection through the material 21 in the groove 3 belowthe tool member 13. The material 21 forward of the projection 15 issubjected to an additional compressive stress which, in combination withthe overall compressive stress acting in the material 21 causesextrusion through the die insert 16.

In all the embodiments, the fit of the abutment member in the groove isnot necessarily critical. Some material may extrude as flash throughclearances but since such flash will be largely the outer skin in thecase of a solid feed the separation of this skin from the product mayeven be advantageous if the feed has surface impurities. It will furtherbe appreciated that the groove shape need not be square or rectangular;instead of the side walls being parallel they may be angled and form,for example, a truncated V groove.

I claim:

1. A process of continuously extruding metal which comprises the stepsof feeding metal into one end of a passageway formed beteen a firstmember and a second member with the second member having a greatersurface area for engaging the metal than the first member, saidpassageway having a closed end remote from said one end and having diemeans at said closed end, and moving the second member relative to thefirst member in a direction towards the die means from said one end tosaid closed end such that the frictional drag of the passageway definingsurfaces of the second member draw the metal through the passageway andthrough the die means.

2. A process according to claim 1 wherein said passageway is formedbetween a wheel member having an endless groove therein and a shoemember covering a part of the length of the groove, and wherein thewheel member is rotated in a direction to drag metal through thepassageway and the die means.

3. Extrusion apparatus comprising first and second members defining anelongate passageway therebetween, said first and second members beingmovable one relative to the other in the direction of the length of thepassageway, an abutment member fixed relative to said second memberprojecting into and blocking the passageway, means defining at least onedie orifice leading from the passageway adjacent the abutment member,said orifice extending from said passageway to a point outside saidapparatus whereby material fed to said apparatus is extrudedtherethrough, means for continuously feeding material to be extrudedfrom a position outside said apparatus into said passageway at a pointspaced from the abutment member, the amount of the surface area of thepassageway defined by the first member which is movable towards theabutment member being greater than the amount of the surface area of thepassageway defined by the second member,

whereby material fed into the passageway is moved by frictional dragwith the surfaces of the passageway in the first member towards theabutment member and is thereby extruded through the die orifice.

4. Extrusion apparatus comprising a wheel member having an endlessgroove therein, a shoe member covering part only of the length of thegroove and forming a passageway therewith, an abutment member projectingfrom the shoe member into the groove and blocking one end of thepassageway, the wheel member being rotatable relative to the shoe memberin the direction towards the abutment member, at least one die orificeadjacent the abutment member, and means for feeding material to beextruded into the end of the passageway remote from the abutment memberso that the material is carried along in the groove by frictional dragin the direction towards the abutment member and is thereby extrudedthrough the die orifice.

5. Extrusion apparatus according to claim 4 wherein the groove is ofuniform cross sectional shape throughout its length and is defined by asurface of revolution about the axis of the wheel member.

6. Extrusion apparatus according to claim 4 wherein the groove is formedcircumferentially in the outer edge of the wheel member.

7. Extrusion apparatus according to claim 3, in which the passageway hasa uniform cross sectional shape throughout its length.

8. Extrusion apparatus as claimed in claim 3, wherein said die orificeis provided in the leading face of the abutment member.

9. Extrusion apparatus as claimed in claim 3, wherein a multiplicity ofdie orifices are provided in the leading face of the abutment member.

10. Extrusion apparatus as claimed in claim 4 wherein said abutmentmember is of solid form, said die orifice being provided in the face ofthe shoe member in front of the abutment member.

11. Extrusion apparatus as claimed in claim 4 wherein a multiplicity ofdie orifices are provided in the face of the shoe member forward of thesolid abutment member.

12. Extrusion apparatus as claimed in claim 4 wherein the deviceincludes a plurality of shoe members co-operating with the groove atspaced intervals, each of said shoe members forming a said passageway.

13. Extrusion apparatus as claimed in claims 4 wherein a tool memberhaving a material working face is provided for operation on material inthe groove of the wheel member in the region adjacent the abutmentmember, means being provided for moving said tool member in a closedcyclic path so that the material in the groove adjacent the abutmentmember is subjected to additional compressive stress by the working faceof the tool member whereby the material is extruded through the dieorifice under the influence of the additional compressive stress incombination with the bulk compressive stress set up in the materialwithin the groove by rotation of the wheel member.

14. Extrusion apparatus as claimed in claim 4 wherein a rotary toolmember having an end face with a tooth member projecting therefrom and adie orifice associated with the tooth member is fitted in a housing inthe shoe member with the end face of the tool member open to the regionof the groove adjacent the face of the abutment member, means beingprovided for rotating the tool member about its axis transverse to theend face having the projecting tooth member so that the tooth member ismoved in a circular path with its forward working face in pressurecontact with the material in the region of the groove adjacent the faceof the abutment member whereby the material forward of the working faceof the tooth member is subjected to an additional compressive stress sothat the material is extruded through the die orifice under theinfluence of the additional compressive stress in combination with thebulk compressive stress set up in the material within the groove byrotation of the wheel member.

15. Extrusion apparatus as claimed in claim 14 wherein a guide member isprovided for distributing to the end face of the rotary tool member, thematerial in the region of the groove adjacent the face of the abutmentmember, said guide member having a wedge shaped base which is located atthe bottom of the groove and tapering away from the face of the abutmentmember, the base of the guide member having an upstanding boss the endface of which bears centrally on the end face of the tool member so thatthe tooth member which projects from the end face thereof rotates aroundthe end of the boss of the guide member as the tool member is rotated.

1. A process of continuously extruding metal which comprises the stepsof feeding metal into one end of a passageway formed between a firstmember and a second member with the second member having a greatersurface area for engaging the metal than the first member, saidpassageway having a closed end remote from said one end and having diemeans at said closed end, and moving the second member relative to thefirst member in a direction towards the die means from said one end tosaid closed end such that the frictional drag of the passageway definingsurfaces of the second member draw the metal through the passageway andthrough the die means.
 2. A process according to claim 1 wherein saidpassageway is formed between a wheel member having an endless groovetherein and a shoe member covering a part of the length of the groove,and wherein the wheel member is rotated in a direction to drag metalthrough the passageway and the die means.
 3. Extrusion apparatuscomprising first and second members defining an elongate passagewaytherebetween, said first and second members being movable one relativeto the other in the direction of the length of the passageway, anabutment member fixed relative to said second member projecting into andblocking the passageway, means defining at least one die orifice leadingfrom the passageway adjacent the abutment member, said orifice extendingfrom said passageway to a point outside said apparatus whereby materialfed to said apparatus is extruded therethrough, means for continuouslyfeeding material to be extruded from a position outside said apparatusinto said passageway at a point spaced from the abutment member, theamount of the surface area of the passageway defined by the first memberwhich is movable towards the abutment member being greater than theamount of the surface area of the passageway dEfined by the secondmember, whereby material fed into the passageway is moved by frictionaldrag with the surfaces of the passageway in the first member towards theabutment member and is thereby extruded through the die orifice. 4.Extrusion apparatus comprising a wheel member having an endless groovetherein, a shoe member covering part only of the length of the grooveand forming a passageway therewith, an abutment member projecting fromthe shoe member into the groove and blocking one end of the passageway,the wheel member being rotatable relative to the shoe member in thedirection towards the abutment member, at least one die orifice adjacentthe abutment member, and means for feeding material to be extruded intothe end of the passageway remote from the abutment member so that thematerial is carried along in the groove by frictional drag in thedirection towards the abutment member and is thereby extruded throughthe die orifice.
 5. Extrusion apparatus according to claim 4 wherein thegroove is of uniform cross sectional shape throughout its length and isdefined by a surface of revolution about the axis of the wheel member.6. Extrusion apparatus according to claim 4 wherein the groove is formedcircumferentially in the outer edge of the wheel member.
 7. Extrusionapparatus according to claim 3, in which the passageway has a uniformcross sectional shape throughout its length.
 8. Extrusion apparatus asclaimed in claim 3, wherein said die orifice is provided in the leadingface of the abutment member.
 9. Extrusion apparatus as claimed in claim3, wherein a multiplicity of die orifices are provided in the leadingface of the abutment member.
 10. Extrusion apparatus as claimed in claim4 wherein said abutment member is of solid form, said die orifice beingprovided in the face of the shoe member in front of the abutment member.11. Extrusion apparatus as claimed in claim 4 wherein a multiplicity ofdie orifices are provided in the face of the shoe member forward of thesolid abutment member.
 12. Extrusion apparatus as claimed in claim 4wherein the device includes a plurality of shoe members co-operatingwith the groove at spaced intervals, each of said shoe members forming asaid passageway.
 13. Extrusion apparatus as claimed in claims 4 whereina tool member having a material working face is provided for operationon material in the groove of the wheel member in the region adjacent theabutment member, means being provided for moving said tool member in aclosed cyclic path so that the material in the groove adjacent theabutment member is subjected to additional compressive stress by theworking face of the tool member whereby the material is extruded throughthe die orifice under the influence of the additional compressive stressin combination with the bulk compressive stress set up in the materialwithin the groove by rotation of the wheel member.
 14. Extrusionapparatus as claimed in claim 4 wherein a rotary tool member having anend face with a tooth member projecting therefrom and a die orificeassociated with the tooth member is fitted in a housing in the shoemember with the end face of the tool member open to the region of thegroove adjacent the face of the abutment member, means being providedfor rotating the tool member about its axis transverse to the end facehaving the projecting tooth member so that the tooth member is moved ina circular path with its forward working face in pressure contact withthe material in the region of the groove adjacent the face of theabutment member whereby the material forward of the working face of thetooth member is subjected to an additional compressive stress so thatthe material is extruded through the die orifice under the influence ofthe additional compressive stress in combination with the bulkcompressive stress set up in the material within the groove by rotationof the wheel member.
 15. Extrusion apparatus as claimed in claim 14wherein a guide member is provided for dIstributing to the end face ofthe rotary tool member, the material in the region of the grooveadjacent the face of the abutment member, said guide member having awedge shaped base which is located at the bottom of the groove andtapering away from the face of the abutment member, the base of theguide member having an upstanding boss the end face of which bearscentrally on the end face of the tool member so that the tooth memberwhich projects from the end face thereof rotates around the end of theboss of the guide member as the tool member is rotated.